In medical implants industry, there is a strong necessity for the development of nanoporous, biodegradable polymeric thin films to serve as drug eluting nanosystems and tailoring of their properties for controlled drug delivery and release. The existing technology for drug eluting implants enables mostly either the development of polymeric matrices loaded with drugs or the formation of pores or reservoirs with micrometer dimensions onto the implant surfaces [1-3]. Hence, such microporosity hinders the sustained and controlled release of the drug at the diseased site which is essential for the optimal rate and dose regimen.
Especially, in the case of drug eluting stents (DES), the medical device comprises a basecoat polymeric matrix loaded with anti-proliferative drugs deposited onto stent surface and a top coat to serve as diffusion barrier for drug release [4]. A wide range of biomaterials both bioabsorbable and biostable ones have been reported as drug eluting coatings that have encapsulated the therapeutic agents/drugs by applying, though not limited, the dipping, spraying, spincoating technologies [4, 5].
Up to date, diverse drugs for local delivery from DES surface have been reported, including anti-proliferative agents, such as rapamycin, paclitaxel, everolimus, zotarolimus, colchicine, ACE inhibitors, anti-inflammatory drugs and anti-oxidants,—such as corticosteroids, statins, probucol—, anti-platelet and anti-coagulant drugs,—such as corticosteroids heparin and heparin fragments, hirudin, aspirin, dypiridamole, platelet GP IIb/IIIa receptor antagonists, ticlopidine, clopidogrel—and genes. However, late thrombosis, inflammation, hypersensitivity reactions and endothelium healing delay are of major concern [6-8].
Indeed, it has been shown that the excessive burst release of drugs from implant surface and non-biodegradable polymer coatings employed by DES impair stent strut endothelialisation and may induce late stent thrombosis.